Alignment weight for floating pin field design

ABSTRACT

An alignment weight is provided. The alignment weight includes a body of material having first and second opposing surfaces. A number of depressions are formed in the first surface. The depressions receive pins of a floating pin field when placed on a floating pin field during connection of the floating pin field to a printed circuit board.

[0001] This application is a continuation of U.S. patent applicationSer. No. 09/754,714, filed Jan. 4, 2001, which is a divisional of U.S.patent application Ser. No. 09/288,486, filed Apr. 8, 1999, which is nowU.S. Pat. No. 6,206,272, which are incorporated herein by reference.

TECHNICAL FIELD OF THE INVENTION

[0002] Embodiments described herein relate generally to the field ofelectronic circuits and, in particular, to an alignment weight for anelectronic circuit with a floating pin field design.

BACKGROUND

[0003] Integrated circuits are a common part of modern electronicequipment. Integrated circuits typically include a large number oftransistors and other circuit elements that are interconnected on acommon semiconductor chip or die. Typically, integrated circuits arepackaged independently and interconnected on a printed circuit board forinstallation in an electronic system, such as a computer.

[0004] A printed circuit board can be connected to an electronic systemin a number of ways. For example, a printed circuit board can include a“floating pin field” on one side of the printed circuit board. Thefloating pin field includes a number of pins that are held in a fixedspatial relation by a pin field carrier through which the pins pass. Thepins are electrically connected to circuit elements on the printedcircuit board. A floating pin field design may be used, for example,with a printed circuit board containing an upgraded processor for acomputer.

[0005] When a floating pin field design is used, the printed circuitboard may be connected to a system through a socket such as a socketlocated on a mother board of a computer system. The socket typicallyincludes a number of receptacles that are placed around a perimeter ofthe socket. The receptacles receive the pins of the floating pin field.

[0006] One problem with printed circuit boards that use a floating pinfield design may arise when pins are soldered to the bottom of theprinted circuit board. Generally, the pins are held in place with a pinfield carrier. The printed circuit board is patterned with solder pasteat the locations where the pins are to connect to the printed circuitboard. The pins and the pin field carrier are placed on the board andthe solder undergoes a reflow process. Unfortunately, sometimes not allof the solder joints created with this reflow process provide acceptableconnection between the pin and the circuit elements on the printedcircuit board. So-called “solder bridges”—solder material that extendsover a significant distance between a pin and the printed circuitboard—can be formed, for example, when a pin moves away from the printedcircuit board during the reflow process. These solder bridges provide apoor, brittle mechanical connection for the pin and can lead to opensolder joints during use. Furthermore, when an open solder joint isdetected after production, the part is typically thrown away sincerework of the open solder joints is overly burdensome. This can resultin a significant waste of resources when fabricating electronic modulesusing floating pin fields.

[0007] For the reasons stated above, and for other reasons stated belowwhich will become apparent to those skilled in the art upon reading andunderstanding the present specification, there is a need in the art fora more reliable technique for producing acceptable solder joints in anelectronic module using a floating pin field design.

SUMMARY

[0008] The above mentioned problems with electronic modules using afloating pin field design and other problems are addressed by thevarious embodiments disclosed, as will be understood by reading andstudying the following specification. An alignment weight is describedthat may be used to hold the pins in place during a reflow process.

[0009] In an embodiment, an alignment weight is provided. The alignmentweight includes a body of material having first and second opposingsurfaces. A number of depressions are formed in the first surface. Thedepressions receive pins of a floating pin field when placed on afloating pin field during connection of the floating pin field to aprinted circuit board.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 is a perspective view of an illustrative embodiment of analignment weight according to the teachings of various embodiments.

[0011]FIG. 2 is a bottom view of the alignment weight of FIG. 1.

[0012]FIG. 3 is a cross-sectional view of a portion of an electronicmodule during production with an alignment weight in place according tovarious embodiments.

[0013]FIG. 4 is a perspective view of an electronic system module with afloating pin field constructed using the alignment weight according tovarious embodiments.

DETAILED DESCRIPTION

[0014] The following detailed description refers to the accompanyingdrawings which form a part of the specification. The drawings show, andthe detailed description describes, specific illustrative embodiments.These embodiments are described in sufficient detail to enable thoseskilled in the art to practice the teachings disclosed herein. Otherembodiments may be used and logical, mechanical and electrical changesmay be made without departing from the scope of the disclosure. Thefollowing detailed description is, therefore, not to be taken in alimiting sense.

[0015]FIG. 1 is a perspective view of an alignment weight indicatedgenerally at 100 and constructed according to the teachings of variousembodiments. Alignment weight 100 is used in a process for connectingpins of a floating pin field to a printed circuit board. Specifically,alignment weight 100 is designed to provide a downward force that helpsto secure pins in place during a solder reflow process and to maintainthe pins in a substantially straight-up alignment. Advantageously,alignment weight 100 also maintains the ends of the pins of the floatingpin field substantially in the same plane.

[0016] Alignment weight 100 is formed from a material that can withstandthe heat of a solder reflow process without significant warping.Further, the material has sufficient weight to provide downward force onthe pins to assure the creation of an acceptable solder joint. Forexample, in one embodiment, alignment weight 100 is formed from Ultem®PolyEtherImide material, e.g., Ultem®2300, commercially available fromEnsiger Corporation. Ultem® PolyEtherImide is an amber transparent highperformance polymer which combines high strength and rigidity atelevated temperatures with long term heat resistance. Other appropriatematerials can be used to produce the body of alignment weight 100.

[0017] Alignment weight 100 includes first and second opposing surfaces104 and 106, respectively. Surface 106 includes a number of depressions108. Depressions 108 are disposed in surface 106 in positions thatcorrespond to the locations of pins in a floating pin field to be usedwith alignment weight 100. In one embodiment, depressions 108 aredisposed in rows around the perimeter of surface 106 as shown in FIGS. 1and 2. However, it is understood that depressions 108 can be disposed atother locations on surface 106 so as to accommodate the layout of otherfloating pin field designs.

[0018] The size of depressions 108 may be selected to assure propervertical alignment of the pins of the floating pin field. For example,when the pins have a diameter of approximately 0.01±0.001 inches,depressions 108 may be formed with an outer diameter at surface 106 ofabout 0.065 inches with an interior angle of 82 degrees and an innerdiameter of about 0.055 inches.

[0019] Alignment weight 100 further includes holes 110 that extendthrough a thickness of alignment weight 100 in center region 107. Holes110 allow heat to flow through alignment weight 100 toward a printedcircuit board located below alignment weight 100 during a reflowprocess. This allows elements other than pins to be soldered beneath thealignment weight when the pins are soldered in place.

[0020] In some embodiments, holes 110 are laid out in an array in centerregion 107. However, it is understood that holes 110 can be located atother positions in alignment weight 100. Further, holes 110 are shown ascylindrical passages through alignment weight 100. Holes 110 can,however, have different sizes and shapes and are not limited to theembodiment shown. In some embodiments, the holes 110 can be omitted whenonly pins are soldered during a reflow process and no other elements areplaced on printed circuit board 304 beneath alignment weight 100.

[0021]FIG. 3 is a cross-sectional view of a portion of an electronicmodule 300 during production with alignment weight 100 in placeaccording to various embodiments. Alignment weight 100 may be used toassure proper contact between pins 302 and printed circuit board 304 atsolder contacts 306. Advantagously, alignment weight 100 can be used tomaintain the ends 314 of pins 302 in substantially the same plane. Thisreduces the likelihood that solder bridges will form at the base of anyof pins 302.

[0022] The pins 302 may be held in a fixed alignment by the fieldcarrier 308, which may be formed from flame retardant 4 (FR4) materialwith holes for receiving pins 302. Field carrier 308 may hold the pins302 in a position that is substantially normal to surface 307 of fieldcarrier 308. The floating pin field 310 may comprise the pins 302 andthe field carrier 308.

[0023] The floating pin field 310 may be placed in contact with screenprinted solder paste on surface 312 of printed circuit board 304 atconnection points for pins 302. With the floating pin field 310 inplace, alignment weight 100 may be placed over the ends 314 of the pins302 such that depressions 108 align with the ends 314 of the pins 302.Electronic module 300 along with alignment weight 100 may undergo asolder reflow process to form the contacts 306. The alignment weight 100may then be removed.

[0024] As shown in FIG. 4, additional circuit components 400 can becoupled to the printed circuit board 304 using, for example, surfacemount technology. For example, an upgraded microprocessor can be coupledto the printed circuit board for insertion into a computer system on theprinted circuit board 304.

[0025] Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat any arrangement which is calculated to achieve the same purpose maybe substituted for the specific embodiments shown. Such applications areintended to cover any adaptations or variations of the variousembodiments. For example, the alignment weight can be used with floatingpin fields for electronic modules other than a processor upgrade.Further, the location, depth, diameter, and interior angle of thedepressions 108 can be varied as necessary for a particular pin field.Further, the alignment weight 100 can be formed without holes 110.Further, circuit components 400 can be coupled to both sides of theprinted circuit board 304. Other materials that are resistant to warpingat elevated temperatures and that provide sufficient weight to aid inimproving the solder bonds can be used for the alignment weight 100 inplace of the Ultem® PolyEtherImide material described above. Otherbonding materials can be used in place of solder to connect the pins 302to the printed circuit board 304.

[0026] This detailed description is not to be taken in a limiting sense,and the scope of various embodiments is defined only by the appendedclaims, along with the full range of equivalents to which such claimsare entitled. Thus, although specific embodiments have been illustratedand described herein, it should be appreciated that any arrangementcalculated to achieve the same purpose may be substituted for thespecific embodiments shown. This disclosure is intended to cover any andall adaptations or variations of various embodiments of the invention.Combinations of the above embodiments, and other embodiments notspecifically described herein, will be apparent to those of skill in theart upon reviewing the above description.

[0027] The Abstract of the Disclosure is provided to comply with 37C.F.R. § 1.72(b), requiring an abstract that will allow the reader toquickly ascertain the nature of the technical disclosure. It issubmitted with the understanding that it will not be used to interpretor limit the scope or meaning of the claims. In addition, in theforegoing detailed description, it can be seen that various features aregrouped together in a single embodiment for the purpose of streamliningthe disclosure. This method of disclosure is not to be interpreted asreflecting an intention that the claimed embodiments of the inventionrequire more features than are expressly recited in each claim. Rather,as the following claims reflect, inventive subject matter lies in lessthan all features of a single disclosed embodiment. Thus the followingclaims are hereby incorporated into the detailed description, with eachclaim standing on its own as a separate preferred embodiment.

What is claimed is:
 1. An alignment weight, comprising: a body having afirst opposing surface and a second opposing surfaces; and a number ofdepressions formed in the first opposing surface so as to receive pinsof a floating pin field when placed on the floating pin field duringconnection of the floating pin field to a printed circuit board, whereinselected ones of the number of depressions are configured to receiveonly one of the pins.
 2. The alignment weight of claim 1, wherein thenumber of depressions are formed in rows along a perimeter of the body.3. The alignment weight of claim 1, wherein the body comprises amaterial that exhibits substantially no warping during a solder reflowprocess.
 4. The alignment weight of claim 1, wherein the body furtherincludes a number of holes that pass through a thickness of the body. 5.The alignment weight of claim 4, wherein the holes are disposed in acenter region of the first opposing surface of the body.
 6. Thealignment weight of claim 1, wherein the depressions have a diameter ata surface of the body that is greater than a diameter of the depressioninside the body.
 7. An alignment weight, comprising: a body having afirst opposing surface and a second opposing surfaces; and a pluralityof depressions formed in the first opposing surface so as to receivepins of a floating pin field when placed on the floating pin fieldduring connection of the floating pin field to a printed circuit board,wherein each of the plurality of depressions are configured to receiveonly one of the pins of the floating pin field, and wherein the body hasa weight sufficient to provide a downward force to secure the pins ofthe floating pin field in place during a solder reflow process and tomaintain the pins of the floating pin field in a substantiallystraight-up alignment.
 8. The alignment weight of claim 1, wherein someof the plurality of depressions have an inner diameter smaller than anouter diameter.
 9. The alignment weight of claim 1, wherein some of theplurality of depressions have an interior angle of less than about 90degrees.
 10. The alignment weight of claim 1, wherein some of theplurality of depressions are substantially circular.
 11. An apparatus,comprising: an alignment weight; a circuit board; and a plurality ofpins adjacent the circuit board and a corresponding plurality ofdepressions in the alignment weight.
 12. The apparatus of claim 11,further comprising: a field carrier coupled to the plurality of pins.13. The apparatus of claim 11, wherein the alignment weight furtherincludes a plurality of passages that pass through a thickness of thealignment weight.
 14. The apparatus of claim 13, wherein the pluralityof passages are disposed in a center region of a first opposing surfaceof the alignment weight.
 15. The apparatus of claim 11, wherein thealignment weight comprises a body having a first opposing surface and asecond opposing surfaces, wherein the body has a plurality of passagesextending from the first opposing surface to the second opposing surfaceand located in a center region of the first opposing surface, whereinthe corresponding plurality of depressions are disposed in rows about aperimeter of the first opposing surface and configured to receive onlyone pin of the plurality of pins.
 16. The apparatus of claim 11, whereinsome of the corresponding plurality of depressions have a diameter at asurface of the body that is greater than a diameter of inside the body.